"Fonts" and shutdowns are not exclusive to operating systems and versions of Indesign. Are you using a font manager? Are you using free downloaded fonts? If you answered yes to both, then try isolating the problematic fonts by deactivating suspects and monitoring performance. Also, there are third party utilities that can clean application font cache, and possible help resolve issue. And, installing an older version of java can help resolve issues with El Capitan and CS6.